At DiskEng we believe that there are two types of hard drives. There is the hard drive that has failed and there is the hard drive that is yet to fail. The only way to minimise the effects of this and any data loss is to always keep a regular backup and never in the same location.

Hard drives are essentially made of four different parts they are built from finely engineered mechanisms. These are the disk controller on the back of the hard drive, internally read/write heads, motor assembly and the disk platters. Each of these parts must be in full working order for the hard drive to function correctly and consistently.

Disk Controller

The electronic disk controller has several functions. It provides the communication interface between the computer and the hard disk. It supplies power to the disk motor which spins the disk platters and it controls the read/write heads when data read or write requests are made by the computer.

Failure of a disk controller can occur due to excess temperature, power spike, firmware damage, component malfunction or physical damage. The result of this will render the hard disk completely inaccessible. If this happens and the disk controller has failed avoid powering the hard disk as this can cause further damage to electronic components and cause erratic behavior of the internal read/write heads causing damage to your data.

Read/Write Heads

The internal head assembly can consist of multiple heads mounted on head arms, one set for each platter surface used to store data. The heads provide access to the disk platters for calibration during power up and for reading data and writing data during normal operation.

Failure of the read/write heads can occur due to physical knocks during operation, erratic behavior due to disk controller failure and misalignment of the head spindle due to excess temperature. If this happens clicking noises will be heard during power up. The disk must be switched off immediately, the result of continues clicking and banging will certainly lead to a physical head crash, completely destroying the hard disk and any data.

Motor Assembly

The hard disk motor assembly is a sealed unit fitted with a DC motor, its only purpose is to spin the disk platters to a fixed speed, this can be 4800, 5200 or 7200 rpm and 10000 or 15000 rpm for high end SCSI hard disks. This precision fixed speed is fundamental for the correct operation of the hard disk.

Failure of the disk motor can occur due to excess temperature resulting in motor seizure, or excess power applied to the motor by a failing disk controller resulting in the motor windings burning out. If this happens the disk will not spin or may emit a beeping or chirping sound. This will render the drive completely inaccessible and will require an involved recovery solution. Continuous powering of the disk may cause additional head failure.

Disk Platters

The internal disk platters are precision aluminum or recently glass cylindrical surfaces coated with a magnetic layer and polished to a mirror appearance. The magnetic layer is organised during manufacture and formatted before the disk is ready for data storage. The platter surfaces contain the stored data as magnetic bit patterns. The disk platter is the most important part of the disk containing the stored data.

Failure of the disk platters can occur if the read/write heads come into contact with the disk surfaces whilst spinning. Under normal operation the heads would be "flying" above the surfaces at a precise distance apart. knocks during operation can cause uncontrolled head oscillation and head bounce damaging the magnetic layer. This would normally lead to a physical head crash and completely destroy the hard disk including any data.